Field of the Invention
The present disclosure relates to an organic light-emitting diode (OLED) display panel and a method of fabricating the same.
Description of Related Art
In the flat panel display industry, liquid crystal display (LCD) devices have been widely used since they are light and consume less power. However, LCD devices have limited abilities in terms of brightness, contrast ratio, viewing angles, size, and the like, since they are non-emissive devices that do not emit light by themselves.
In order to overcome these problems of LCD devices, new flat display devices have been actively developed. Organic light-emitting diode (OLED) display devices, one type of new flat display devices, have advantages of high luminance levels, wide viewing angles, and high contrast ratios compared to LCD devices, since OLEDs able to emit light by themselves are used therein. In addition, OLED display devices can have a light and thin profile and consume less power, since they do not require a backlight.
An OLED display panel of an OLED display device displays an image using light emitted from OLEDs connected to thin-film transistors (TFTs) in each pixel area. OLEDs are a device in which an organic compound forms an organic light-emitting layer between the anode and the cathode to emit light when an electric field is applied thereto. OLEDs have many advantages such as operability at low voltages, relatively low power consumption, a low weight, and fabricability on a flexible substrate.
OLEDs are grouped into a top emission (or front emission) type and a bottom emission (or back emission) type. Top emission OLEDs require high levels of light transmittance and high electrical conductivity for a cathode. However, the use of a transparent material for the cathode has an adverse effect on electrical conductivity characteristics due to the high sheet resistance, whereas the addition of a metal layer intended to improve electrical conductivity reduces light transmittance instead.
A protective layer protecting the internal devices of an OLED display device has limited impermeability properties when it is formed of a single layer or a thin film, and therefore cannot effectively protect the interior from moisture and oxygen. In contrast, when a multilayer structure is employed to improve the permeability of the protective layer, it is problematic in that light transmittance is reduced, processing is complicated, the number of process steps is increased, and consequently manufacturing costs are increased.
In addition, when OLED display devices are flexible display devices, it is difficult to ensure that the layers have mechanical flexibility when forming layers by vapor deposition.